import typing


def _ceil_pow2(n: int) -> int:
    x = 0
    while (1 << x) < n:
        x += 1

    return x


class SegTree:
    def __init__(self,
                 op: typing.Callable[[typing.Any, typing.Any], typing.Any],
                 e: typing.Any,
                 v: typing.Union[int, typing.List[typing.Any]]) -> None:
        self._op = op
        self._e = e

        if isinstance(v, int):
            v = [e] * v

        self._n = len(v)
        self._log = _ceil_pow2(self._n)
        self._size = 1 << self._log
        self._d = [e] * (2 * self._size)

        for i in range(self._n):
            self._d[self._size + i] = v[i]
        for i in range(self._size - 1, 0, -1):
            self._update(i)

    def set(self, p: int, x: typing.Any) -> None:
        assert 0 <= p < self._n

        p += self._size
        self._d[p] = x
        for i in range(1, self._log + 1):
            self._update(p >> i)

    def get(self, p: int) -> typing.Any:
        assert 0 <= p < self._n

        return self._d[p + self._size]

    def prod(self, left: int, right: int) -> typing.Any:
        assert 0 <= left <= right <= self._n
        sml = self._e
        smr = self._e
        left += self._size
        right += self._size

        while left < right:
            if left & 1:
                sml = self._op(sml, self._d[left])
                left += 1
            if right & 1:
                right -= 1
                smr = self._op(self._d[right], smr)
            left >>= 1
            right >>= 1

        return self._op(sml, smr)

    def all_prod(self) -> typing.Any:
        return self._d[1]

    def max_right(self, left: int,
                  f: typing.Callable[[typing.Any], bool]) -> int:
        assert 0 <= left <= self._n
        assert f(self._e)

        if left == self._n:
            return self._n

        left += self._size
        sm = self._e

        first = True
        while first or (left & -left) != left:
            first = False
            while left % 2 == 0:
                left >>= 1
            if not f(self._op(sm, self._d[left])):
                while left < self._size:
                    left *= 2
                    if f(self._op(sm, self._d[left])):
                        sm = self._op(sm, self._d[left])
                        left += 1
                return left - self._size
            sm = self._op(sm, self._d[left])
            left += 1

        return self._n

    def min_left(self, right: int,
                 f: typing.Callable[[typing.Any], bool]) -> int:
        assert 0 <= right <= self._n
        assert f(self._e)

        if right == 0:
            return 0

        right += self._size
        sm = self._e

        first = True
        while first or (right & -right) != right:
            first = False
            right -= 1
            while right > 1 and right % 2:
                right >>= 1
            if not f(self._op(self._d[right], sm)):
                while right < self._size:
                    right = 2 * right + 1
                    if f(self._op(self._d[right], sm)):
                        sm = self._op(self._d[right], sm)
                        right -= 1
                return right + 1 - self._size
            sm = self._op(self._d[right], sm)

        return 0

    def _update(self, k: int) -> None:
        self._d[k] = self._op(self._d[2 * k], self._d[2 * k + 1])


from itertools import accumulate


class Accum:
    def __init__(self, xs):
        self.acc = list(accumulate(xs))

    def __getitem__(self, i):
        return self.acc[i]

    def range(self, l: int, r: int) -> int:
        """[l, r] の区間和"""
        assert 0 <= l <= r < len(self.acc)
        return self.acc[r] if l == 0 else self.acc[r] - self.acc[l-1]


def bsearch(low: int, high: int, pred) -> int:
    assert pred(low)
    lo = low
    hi = high
    res = low
    while lo <= hi:
        m = (lo + hi) // 2
        if pred(m):
            res = max(res, m)
            lo = m + 1
        else:
            hi = m - 1

    return res


from itertools import pairwise
import operator

INF = 1 << 62
N, L = map(int, input().split())
K = int(input())
A = list(map(int, input().split()))


cakes = []
for a, b in pairwise([0] + A + [L]):
    cakes.append(b-a)
accum = Accum(cakes)


# 2番目に大きな値を m 以上にできるか
def can(m: int) -> bool:
    dp = [[-INF] * 3 for _ in range(len(cakes)+1)]
    dp[0][0] = 0

    for i in range(len(cakes)):
        for j in range(3):
            dp[i+1][j] = max(dp[i+1][j], dp[i][j] + 1)

        # i 番目から m を超える
        lo = i
        hi = len(cakes)-1
        p = INF
        while lo <= hi:
            mid = (lo + hi) // 2
            # x = segt.prod(i, mid+1)
            x = accum.range(i, mid)
            # print(f'{i=} {mid=} : {x=}')
            if x >= m:
                p = min(p, mid)
                hi = mid - 1
            else:
                lo = mid + 1

        if p < len(cakes):
            # print(f'>> {i=} : {p=}')
            for j in range(3-1):
                dp[p+1][j+1] = max(dp[p+1][j+1], dp[i][j] + 1)

    # print(f'{m=} : {dp[N][2]} : {dp[N][2] > K}')
    return dp[len(cakes)][2] > K


ans = bsearch(1, L, can)
print(ans)